Cosmetic composition comprising 2-hydroxyalkenoic acids or a mixture thereof

ABSTRACT

The invention concerns 2-hydroxyalkenoic acids within a general formula ##STR1## where R&#39; is chosen from: 
     a. C w  H 2w , 
     b. C y  H 2y-1 , and 
     c. C y  H 2y  OZ 
     where 
     z is chosen from H, R&#34; and (CH 2 ) n  OR&#34; 
     R&#34; is chosen from C m  H 2m+1  and (CH 2 ) n  OC m  H 2m+1  ; 
     w is an integer of from 1 to 25 
     y is an integer of from 2 to 25 
     m is an integer of from 1 to 4 
     n is an integer of from 1 to 6 
     Many compounds within the formula are novel and are claimed as such. The invention also provides a process for making the compounds, and compositions for topical application to human skin, hair or nails which contain compounds of the above formula and a cosmetically acceptable vehicle.

FIELD OF INVENTION

The invention relates to unsaturated hydroxy acids, particularly2-hydroxyalkenoic acids, to a process for preparing these acids, and totheir use in compositions for topical application to skin, hair andnails.

BACKGROUND AND PRIOR ART i) Compounds per se

Very few 2-hydroxyalkenoic acids have been reported in the literature.These are:

2-hydroxy-4-hexenoic acid, whose synthesis is described in a paper byMikami et al entitled "Novel silyl triflate-mediated [2,3] Wittigsigmatropic rearrangement. The possible interpretation of an oxygenylide", published in Tetrahedron Lett. 1986. 27(37), 4511-14, andabstracted in Chem. Abs. (1987), 107, 77286h.

2-Hydroxy-4-heptenoic acid, whose synthesis is described in a paper byAchmatowicz et al entitled

"Monoenic syntheses. I. On monoenophilic reactivity of ethylmesoxalate", published in Roczniki Chem. 36, 1791-1813 (1962), andabstracted in Chem. Abs. (1963), 59 8610d.

2-Hydroxy-4-octenoic acid, whose synthesis is described in a paper byBrenner et al, entitled "Some aspects of the chemistry of1,1,1-trihaloalk-4-en-ols, the ene adducts obtained from reaction ofchloral and bromal with alkenes", published in J. Chem. Soc., PerkinTrans. 1 1984 (3), 331-42, and abstracted in Chem. Abs. (1984), 101,38095b.

2-Hydroxy-4-dodecenoic acid, whose synthesis is described in a paper byTakeshi et al entitled "Application of [2,3] sigmatropic rearrangementsin organic synthesis. III. The [2,3] Wittig rearrangement of2-alkenyloxyacetic acids and its application to the stereocontrolledsynthesis of β,γ-unsaturated aldehydes and conjugated dienoic acids",published in Tetrahedron Lett. 1981, 22(1), 69-72, and abstracted inChem. Abs. (1981), 95, 6442d.

It is apparent that other 2-hydroxyalkenoic acids have not previouslybeen disclosed in the literature, and an aspect of the invention isaccordingly concerned with certain new 2-hydroxyalkenoic acids, andtheir synthesis.

ii) Cosmetic Compositions

A soft, supple and flexible skin has a marked cosmetic appeal and is anattribute of normal functioning epidermis. The outer layer of theepidermis, i.e. the stratum corneum, can, however, become dry and flakyfollowing exposure to adverse climatic conditions, or excessive contactwith detergents or solvents which result in loss of skin moisture, sothat the skin loses its soft, supple and flexible characteristics.Emollients such as fats, phospholipids and sterols have in the past beenused to soften dry skin, but it is apparent that these emollients areonly partially effective as a remedy for this type of condition. Also,typical application to the skin of classical humectants is unlikely toalleviate this problem since they are not particularly skin substantiveand are generally rinsed from the skin during washing.

It is therefore evident that there exists a need for an effectivetreatment for skin which is in a dry, flaky condition and which isrelatively inflexible.

It has been proposed in U.S. Pat. No. 4,105,782 (Yu & Van Scott) to useamides or ammonium salts of α-hydroxyacids in the treatment of acne ordandruff and, in the Yu & Van Scott patents, U.S. Pat. No. 4,105,783 andU.S. Pat. No. 4,197,316, to use such compounds in the treatment of dryskin. U.S. Pat. No. 4,234,599 (Yu & Van Scott) discloses the use ofα-hydroxyacids, and their esters or amine salts in the treatment ofkeratoses.

In U.S. Pat. No. 4,363,815 (Yu & Van Scott) it is proposed to useα-hydroxyacids or β-hydroxyacids or ketoacids or their derivatives,including inorganic salts, in a composition for treating skinconditions.

According to GB 1 471 679 (Avon), the use of alkali metal salts of C₂-C₅ α-hydroxycarboxylic acids in moisturising compositions is proposed.

In DE 2 110 993 (Henkel), there are disclosed alkali metal salts of C₄-C₁₀ α-hydroxycarboxylic acids, and the sodium salt of α-hydroxycaprylicacid is mentioned. These salts are incorporated in amounts from 3-30%into washing and cleaning compositions and are said to confer improvedstorage stability.

As part of a programme to examine substances for their ability toimprove skin condition, isolated guinea pig footpad stratum corneum wasselected as a model for human skin, and changes in its elasticity weremeasured after application of each test substance. The amount by whichextensibility of the stratum corneum was increased was taken as ameasure of the likely skin benefit that the substance would have onhuman skin.

Of the many substances screened in this way, certain 2-hydroxyalkanoicacids, as described in EP-B-O 007 785 (Unilever), were identified fortheir skin benefits when included in compositions for topicalapplication to the skin. Such benefits include both increased elasticityof the skin, particularly the stratum corneum, and improved appearance.However, difficulty can be experienced when formulating certain of these2-hydroxyalkanoic acids in skin cosmetic formulations, due to their poorsolubility in water.

DEFINITION OF THE INVENTION COMPOUND PER SE

The invention accordingly provides 2-hydroxyalkenoic acid having thestructure (1): ##STR2## where

R is chosen from:

a. C_(x) H_(2x+1),

b. C_(y) H_(2y-1), and

c. C_(y) H_(2y) OZ;

where

Z is chosen from H, R" and (CH₂)_(n) OR"

R" is chosen from C_(m) H_(2m+1) and (CH₂)_(n) OC_(m) H_(2m+1) ;

x is an integer of from 4 to 6, or from 8 to 25

y is an integer of from 2 to 25

m is an integer of from 1 to 4

n is an integer of from 1 to 6.

In further aspects the invention also provides a process for preparingthe unsaturated 2-hydroxyalkenoic acids, and skin, hair and nailtreatment compositions incorporating unsaturated 2-hydroxyalkenoicacids.

DISCLOSURE OF THE INVENTION The 2-hydroxyalkenoic acid

The unsaturated 2-hydroxyalkenoic acid has the structure (1): ##STR3##where

R is chosen from:

a. C_(x) H_(2x+1),

b. C_(y) H_(2y-1), and

c. C_(y) H_(2y) OZ;

where

Z is chosen from H, R" and (CH₂)_(n) OR"

R" is chosen from C_(m) H_(2m+1) and (CH₂)_(n) OC_(m) H_(2m+1) ;

x is an integer of from 4 to 6, or from 8 to 25

y is an integer of from 2 to 25

m is an integer of from 1 to 4

n is an integer of from 1 to 6.

The new 2-hydroxyalkenoic acids in accordance with the genericdefinition given herein are exemplified by three classes of new acids,namely:

mono-unsaturated 2-hydroxyalkenoic acids, di-unsaturated2-hydroxyalkenoic acids, and mono-unsaturated oxa-2-hydroxyalkenoicacids (i.e. ether acids).

Examples of the new mono-unsaturated 2-hydroxyalkenoic acids, where R isC_(x) H_(2x+1) include:

2-Hydroxy-4-nonenoic acid

2-Hydroxy-4-decenoic acid

2-Hydroxy-4-undecenoic acid

2-Hydroxy-4-tridecenoic acid

2-Hydroxy-4-tetradecenoic acid

2-Hydroxy-4-pentadecenoic acid

2-Hydroxy-4-hexadecenoic acid

2-Hydroxy-4-heptadecenoic acid

2-Hydroxy-4-octadecenoic acid

2-Hydroxy-4-nonadecenoic acid

2-Hydroxy-4-eicosenoic acid

2-Hydroxy-4-heneicosenoic acid

2-Hydroxy-4-docosenoic acid

2-Hydroxy-4-tricosenoic acid

2-Hydroxy-4-tetracosenoic acid

2-Hydroxy-4-pentacosenoic acid

2-Hydroxy-4-hexacosenoic acid

2-Hydroxy-4-heptacosenoic acid

2-Hydroxy-4-octacosenoic acid

2-Hydroxy-4-nonacosenoic acid, and

2-Hydroxy-4-triacontencoic acid.

Examples of the new di-unsaturated 2-hydroxyalkenoic acids, where R isC_(y) H_(2y-1) include:

2-Hydroxy-4,7-octadienoic acid

2-Hydroxy-4,9-decadienoic acid

2-Hydroxy-4,10-undecadienoic acid

2-Hydroxy-4,11-dodecadienoic acid

2-Hydroxy-4,13-tetradecadienoic acid

2-Hydroxy-4,15-hexadecadienoic acid

2-Hydroxy-4,17-octadecadienoic acid

2-Hydroxy-4,19-eicosadienoic acid

2-Hydroxy-4,21-docosadienoic acid

2-Hydroxy-4,23-tetracosadienoic acid

2-Hydroxy-4,25-hexacosadienoic acid

2-Hydroxy-4,27-octacosadienoic acid, and

2-Hydroxy-4,29-triacontadienoic acid.

Examples of new mono unsaturated oxa-2-hydroxyalkenoic acids where R isC_(y) H_(2y) OZ (ether acids) include:

2-Hydroxy-6-oxa-4-heptenoic acid

2-Hydroxy-7-oxa-4-octenoic acid

2-Hydroxy-9-oxa-4-decenoic acid

2-Hydroxy-9-oxa-4-undecenoic acid

2-Hydroxy-11-oxa-4-dodecenoic acid

2-Hydroxy-13-oxa-4-tetradecenoic acid

2-Hydroxy-13-oxa-4-pentadecenoic acid

2-Hydroxy-14-oxa-4-pentadecenoic acid

2-Hydroxy-13-oxa-14-methyl-4-pentadecenoic acid

2-Hydroxy-11,14-dioxa-4-pentadecenoic acid

2-Hydroxy-13-oxa-4-hexadecenoic acid

2-Hydroxy-14-oxa-4-hexadecenoic acid

2-Hydroxy-15-oxa-4-hexadecenoic acid

2-Hydroxy-17-oxa-4-octadecenoic acid

2-Hydroxy-14,17-dioxa-4-octadecenoic acid

2-Hydroxy-18-oxa-4-eicosenoic acid

2-Hydroxy-18-oxa-19-methyl-4-eicosenoic acid

2-Hydroxy-19-oxa-4-docosenoic acid

2-Hydroxy-18,21-dioxa-4-tricosenoic acid

2-Hydroxy-22-oxa-4-tetracosenoic acid

2-Hydroxy-25-oxa-4-hexacosenoic acid

2-Hydroxy-24-oxa-4-heptacosenoic acid

2-Hydroxy-25-oxa-4-octacosenoic acid

2-Hydroxy-23,26-dioxa-4-octacosenoic acid, and

2-Hydroxy-29-oxa-4-triacontenoic acid.

It is to be understood that the above examples of 2-hydroxyalkenoicacids are merely illustrative of the many acids covered by the genericstructure (1) given herein before.

PROCESS FOR PREPARING THE 2-HYDROXYALKENOIC ACID

The process for preparing the 2-hydroxyalkenoic acids, as hereindefined, is based on that described by Klimova et al, in a paperentitled "Catalytic monoene synthesis with carbonyl compounds. Additionof 1-alkenes to glyoxylic acid esters", published in Dokl. Akad. NaukSSSR 173 (6), 1332-5 (1967) and abstracted in Chem Abs 67 (1967),108156c.

The process according to the invention therefore comprises, in broadgeneral terms, the steps of catalysing the reaction of an alkene and analkyl glyoxalate to form, as an intermediate, a 2-hydroxyalkenoateester, and subsequently hydrolysing this ester with a base in order toform the corresponding free 2-hydroxyalkenoic acid.

A preferred process for preparing the 2-hydroxy alkenoic acids accordingto the invention involves the use of methyl glyoxalate, as the alkylglyoxalate, and stannic chloride as the catalyst, the alkene having thestructure (2) ##STR4## the options for the group R being as hereindefined for R in structure (1).

This aspect of the invention can accordingly be defined as a process forpreparing a 2-hydroxyalkenoic acid, as defined herein, and having thestructure (1), which process comprises the steps of:

i) catalysing the reaction of an alkene having the structure (2):##STR5## with an alkyl glyoxalate having the structure (3) ##STR6##where R"' is C_(m) H_(2m+1) and m is an integer of from 1 to 4; to forman unsaturated hydroxy ester having the structure (4) ##STR7## and ii)hydrolysing the unsaturated hydroxy ester to yield the corresponding2-hydroxy alkenoic acid having the structure (1) ##STR8##

The steps of a preferred form of this process can be summarised asfollows:

i. Dissolve methyl glyoxalate and the alkene in dichloromethane undernitrogen atmosphere and cool;

ii. Add stannic chloride, stir and allow to warm;

iii. Neutralise with triethylamine, add water and furtherdichloromethane;

iv. Separate organic layer, wash, dry, remove solvent and distill offester product;

v. Hydrolyse ester with base under reflux conditions; and

vi. Wash solution with hexane, acidify solution and extract product, dryand then remove organic solvent to leave either liquid (purifiable bydistillation) or solid (purifiable by crystallisation).

According to a preferred process, employing the above summary, thehydroxyalkenoic acids according to the invention can be prepared asfollows:

Methyl glyoxalate (1.0 equivalents) and the requisite alkene (2.0equivalents) are dissolved in dry dichloromethane under a nitrogenatmosphere. Stannic chloride (0.3 equivalents) is added dropwise withstirring and cooling (ice/water bath at approx 0° C.). After 30 minutesat this temperature, the reaction is allowed to warm to room temperatureand stirred for a further 21 hours. The mixture is neutralised withtriethylamine (0.3 equivalents), stirred for an additional 5 minutesbefore water and dichloromethane are added. The organic layer isseparated, washed in turn with water and brine, dried over anhydrousmagnesium sulphate and evaporated, with the crude product being purifiedby short path distillation to give the pure hydroxy ester.

This intermediate is treated with 20% w/v sodium hydroxide solution(water:methanol, 1:1) and heated under reflux for 1 hour. After thereaction mixture has cooled to room temperature, it is washed withhexane and the organic layer separated. The clear aqueous phase isacidified to pH 1 with concentrated hydrochloric acid, followed byextraction of product with diethylether. The organic layer is separated,washed with brine, dried over anhydrous magnesium sulphate andevaporated to dryness to yield the desired 2-hydroxy-4-alkenoic acid.

These aspects of the invention are further illustrated by the followingExamples which describe synthesis of selected 2-hydroxy-4-alkenoic acidsaccording to the invention and provide also characterising data of thesenew acids.

EXAMPLE 1 Synthesis of 2-Hydroxy-4-octadecenoic acid (5)

The synthesis of this acid is in accordance with the following scheme,in which hexadecene (6) is the alkene starting material. ##STR9##

i. Synthesis of the intermediate methyl 2-hydroxy-4-octadecenoate

Methyl glyoxalate (8.80 g, 0.1 mol, 1.0 eq) and 1-hexadecene (44.80 g,0.2 mol, 2.0 eq) are dissolved in dry dichloromethane (200 ml, freshlydistilled from calcium hydride) under a nitrogen atmosphere. Stannicchloride (3.51 ml, 0.03 mol, 0.3 eq) is added dropwise with stirring andcooling at 0° C. (ice/water bath). After half an hour the reactionmixture is allowed to warm to room temperature and stirred for a further21 hours before being neutralised with triethylamine (4.2 ml, 0.03 mol,0.3 eq) with a further 5 minutes stirring. Water (50 ml) anddichloromethane (100 ml) are added, the organic layer is separated,washed in turn with water (50 ml) and brine (50 ml), dried overanhydrous magnesium sulphate and evaporated. The crude oil is purifiedby short path distillation (bp 220-230° C./0.7 mm Hq) to furnish theester product as a colourless liquid.

ii. Synthesis of 2-hydroxy-4-octadecenoic acid having the structure (5)

Methyl 2-hydroxy 4-octadecenoate (8.21 g, 0.026 mol, 1.0 eq) is heatedunder reflux with a large excess of sodium hydroxide (8.4 g, 0.21 mol,8.1 eq) in water (20 ml) and methanol (20 ml) for 1 hour. After coolingdown to room temperature, the mixture is washed with hexane (50 ml) andthe organic phase separated. The clear aqueous layer is acidified to pH1 with concentrated hydrochloric acid and the resultant mixture isextracted with diethylether (3×50 ml), the combined organic layers beingwashed with brine (50 ml) dried over anhydrous magnesium sulphate andevaporated to give a white solid. This is recrystallised from ethylacetate/hexane to give the product acid (5) as white needles, 6.35 g(81%), mp 78-79.5° C.

Characterising spectral data were as follows:

mp 78-79.5° C.; ^(v) max (nujol) 3440 and 1745 cm⁻¹ ; δ_(H) (360 MHz, d₆-DMSO) 0.90 (3H, t, 18-H₃, CH₃), 1.30 (22H, br s, 7 to 17-H₂, CH₂), 2.05(2H, m, 6-H₂, CH₂ CH═), 2.25-2.40 (2H, 2xm, 3-H₂, CH₂ CHOH), 4.00 (1H,t, 2-H, CHOH) and 5.50 p.p.m. (2H, m, 4 and 5-H, CH═); C.I., M⁺ 298.

EXAMPLE 2 Synthesis of 2-hydroxy-4,9-decadienoic acid (7)

The synthesis of this acid is in accordance with the following scheme,in which 1,7-octadiene (8) is the alkene starting material. ##STR10##

The procedure for the synthesis of methyl 2-hydroxy-4,9-decadienoate,and its conversion to 2-hydroxy-4,9-decadienoic acid were essentially asdescribed in Example 1, except that 1,7-octadiene was used as the alkenein place of hexadecene.

2-Hydroxy-4,9-decadienoic acid had a boiling point of 240-250° C. at 0.6mm Hg, and possessed the following characterising spectral data:

^(v) max (liq film) 3500-2400 (br), 2950, 2920, 1725 (br), 1640, 1440,1380, 1210, 1100, 990, 970 and 720 cm⁻¹ ; δ_(H) (360 MHz, CDCl₃) 1.45(2H, m, 7-H₂, CH₂), 2.05 (4H, m, 6 and 8-H , CH₂ CH═), 2.40 (1H, m, 3-H,CHCHOH), 2.60 (1H, m, 3-H, CHCHOH), 4.30 (1H, t, J=3.3 Hz, 2-H, CHOH),5.00 (2H, m, 8-H₂, CH₂ ═), 5.40 (1H, m, 5-H, CH═), 5.65 (1H, m, 4-H,CH═) and 5.85 p.p.m. (1H, m, 7-H, CH═), C.I.; M⁺ 184.

EXAMPLE 3 Synthesis of 2-hydroxy-13-oxa-4-tetradecenoic acid (9)

The synthesis of this acid is in accordance with the following scheme,in which 11-oxa-1-dodecene (10) is the alkene starting material.##STR11##

The procedure for the synthesis of methyl2-hydroxy-13-oxa-4-tetradecenoate and its conversion to2-hydroxy-13-oxa-4-tetradecenoic acid were essentially as described inExample 1, except that 11-oxa-1-dodecene was used as the alkene in placeof hexadecene.

2-Hydroxy-13-oxa-4-tetradecenoic acid had a melting point of 5-10° C.,and possessed the following characterising spectral data:

^(v) max (liq film) 3400, 2930, 2860, 1720, 1250, 1100 and 970 cm⁻¹ ;δ_(H) (360 MHz, CDCl₃) 1.25 (8H, br m, 7 to 10-H₂, CH₂), 1.55 (2H, m,11-H₂, CH₂ CH₂ O), 2.00 (2H, m, 6-H, CH₂ CH═), 2.40-2.60 (2H, 2×m, 3-H₂,CH₂, CHOH), 3.35 (3H, s, 14-H₃, CH₃ O), 3.40 (2H, t, 2-H₂, CH₂ O), 4.30(1H, t, 2-H, CHOH) and 5.40-5.65 p.p.m. (2H, 2×m, 4 and 5-H, CH═); C.I.,M⁺ 244.

As mentioned, the invention also relates to a composition for topicalapplication to human skin which comprises 2-hydroxy alkenoic acids,including both new acids as herein defined and other acids alreadyreported in scientific literature, but whose utility is far removed fromuse in topical products.

As mentioned above, difficulty can be experienced when formulatingcertain 2-hydroxyalkenoic acids in skin cosmetic, formulations, due totheir poor solubility in water.

It has now surprisingly been discovered that certain 2-hydroxyalkenoicacids are much more soluble in water and are considerably easier toformulate than their corresponding saturated acids. Furthermore, topicalapplication of these unsaturated acids to skin results in a substantialincrease in skin flexibility, so that the pliability of the skin isimproved.

The invention also concerns compositions containing the new2-hydroxyalkenoic acids, as herein defined, which are suited to topicalapplication to human skin, hair and nails. The invention is alsoconcerned with compositions of a similar nature, and having a similaruse, that comprise 2-hydroxyalkenoic acids whose identity have beendisclosed in published literature, but whose reported utility is farremoved from personal care products intended for topical application tohuman skin.

DEFINITION OF THE COMPOSITION OF THE INVENTION

The invention also provides a composition for topical application tohuman skin, hair or nails which comprises:

i. from 0.1 to 99.9% by weight of a 2-hydroxyalkenoic acid having thestructure (20) ##STR12## where

R' is chosen from:

a. C_(w) H_(2w),

b. C_(y) H_(2y-1), and

c. C_(y) H_(2y) OZ

where

Z is chosen from H, R" and (CH₂)_(n) OR"

R" is chosen from C_(m) H_(2m+1) and (CH₂)_(n) OC_(m) H_(2m+1) ;

w is an integer of from 1 to 25

y is an integer of from 2 to 25

m is an integer of from 1 to 4

n is an integer of from 1 to 6; and

ii. from 0.1 to 99.9% by weight of a cosmetically acceptable vehicle forthe acid.

The 2-hydroxyalkenoic acid

The composition according to the invention comprises a 2-hydroxyalkenoicacid or a mixture thereof, having the structure (20) as herein defined.

Examples of these 2-hydroxyalkenoic acids include:

2-hydroxy-4-hexenoic acid

2-hydroxy-4-heptenoic acid,

2-hydroxy-4-octenoic acid, and

2-hydroxy-4-dodecenoic acid.

Further examples of 2-hydroxyalkenoic acids, include the newmono-saturated acids, di-unsaturated acids and mono-unsaturatedoxo-acids as herein defined.

The 2-hydroxyalkenoic acid is present in the composition according tothe invention in an amount of from 0.1 to 90%, preferably from 0.5 to10% and ideally from 1 to 5% by weight of the composition.

Synthesis of 2-hydroxyalkenoic acid

The 2-hydroxyalkenoic acids for use in the composition according to theinvention can be prepared by the method described hereinbefore for thenew 2-hydroxyalkenoic acids.

This aspect of the invention is illustrated by two more Examples whichdescribe the synthesis and characterisation of two further2-hydroxyalkenoic acids having the structure (20).

EXAMPLE 4 Synthesis of 2-Hydroxy-4-octenoic acid (21)

The synthesis of this acid is in accordance with the following scheme,in which 1-hexene (22) is the alkene starting material which is reactedwith methyl glyoxalate to form methyl 2-hydroxy-4-octenoate (23) andthen hydrolysed to form the free acid (21): ##STR13##

i. Synthesis of methyl 2-hydroxy-4-octenoate (23)

Methyl glyoxalate (8.80 g, 0.1 mol, 1.0 eq) and 1-hexene (16.80 g, 0.2mol, 2.0 eq) are dissolved in dry dichloromethane (150 ml, freshlydistilled from calcium hydride) under a nitrogen atmosphere. Stannicchloride (3.51 ml, 0.03 mol, 0.3 eq) is added dropwise with stirring andcooling at 0° C. (ice/water bath). After half an hour the reactionmixture is allowed to warm to room temperature and stirred for a further21 hours before being neutralised with triethylamine (4.2 ml, 0.03 mol,0.3 eq) with a further 5 minutes stirring. Water (50 ml) anddichloromethane (100 ml) are added, the organic layer is separated,washed in turn with water (50 ml) and brine (50 ml), dried overanhydrous magnesium sulphate and evaporated. The crude oil is purifiedby short path distillation (b p 120-130° C./0.7 mm Hg) to furnish theester product (23) as a colourless liquid, 11.49 g (67% yield).

Characterisation spectral data were as follows: ^(v) max (liq film) 3500 (br), 2 960, 2 920, 1740, 1 440, 1 2110 (br), 1090 and 970 cm⁻¹ ;δ_(H) (360 MH_(z), CDCl₃) 0.90 (3H, t, J=8.0 Hz, 8-H₃, CH₃ CH₂), 1.40(2H, m, 7-H₂, CH₂ CH₃), 2.00 (2H, m, 6-H₂, CH₂ CH═), 2.40 (1H, m, 3-H,CHCHOH), 2.50 (1H, m, 3-H, CHCHOH), 2.75 (1H, d, J=6.5 Hz, OH), 3.80(3H,s, CH₃ O), 4.25 (1H, m, 2-H, CHOH), 5.40 (1H, m, 5-H, CH═) and 5.60p.p.m. (1H, m, 4-H, CH═); C.I., M⁺ 172.

ii. Synthesis of 2-hydroxy-4-octenoic acid (21)

Methyl 2-hydroxy-4-octenoate (23)(7.04 g, 0.041 mol, 1.0 eq) is heatedunder reflux with a large excess of sodium hydroxide (13.5 g, 0.34 mol,8.3 eq) in water (30 ml) and methanol (30 ml) for 1 hour. After coolingdown to room temperature, the mixture is washed with hexane (50 ml) andthe organic phase separated. The clear aqueous layer is acidified to pH1 with concentrated hydrochloric acid and the resultant mixture isextracted with diethylether (3×50 ml), the combined organic layers beingwashed with brine (50 ml) thence dried over anhydrous magnesium sulphateand evaporated to give a colourless oil which slowly crystallised tofurnish the product acid (21) as a white waxy solid, 5.72 g (88%), m p37-38° C.

Characterisation spectral data were as follows: ^(v) max (nujol) 3440, 2820, 1695, 1420, 1150, 1095, 1045 and 920 cm⁻¹ ; δ_(H) (360 MH_(z),CDCl₃) 0.90 (3H, t, 8-H, CH₃), 1.40 (2H, m, 7-H₂, CH₃ CH₂), 2.00 (2H, m,6-H₂, CH₂ CH═), 2.40-2.60(2H,m,3-H₂, CH₂ CHOH), 4.30 (1H, t, CHOH), 5.40(1H, m, 5-H, CH═) and 5.60 p.p.m. (1H, m, 4-H, CH═); C.I., M⁺ 158.

EXAMPLE 5 Synthesis of 2-Hydroxy-4-dodecenoic acid (24)

The synthesis of this acid is in accordance with the following scheme,in which 1-decene (25) is the alkene starting material. ##STR14##

The procedure for the synthesis of methyl 2-hydroxy-4-dodecenoate, andits conversion to 2-hydroxy-4-dodecenoic acid were essentially asdescribed in Example 4, except that 1-decene was used on the alkene inplace of 1-hexene.

2-Hydroxy-4-dodecenoic acid had a melting point of 45-48° C. andpossessed the following characterising spectral data:

^(v) max (nujol) 3440, 3200-2500 (br), 1740, 1090, 965 and 720 cm⁻¹ ;δ_(H) (360 MH_(z), CDCl₃) 0.90 (3H, t, 12-H₃, CH₃), 1.20-1.40 (10 H, m,7 to 11-H₂, CH₂), 2.00 (2H, m, 6-H₂, CH₂ CH═), 2.45 (1H, m, 3-H,CHCHOH), 2.55 (1H, m, 3-H, CHCHOH), 4.30 (1H, t, 2-H, CHOH), 5.40 (1H,m, 5-H, CH═) and 5.60 p.p.m. (1H, m, 4-H, CH═); F.A.B., M⁺ 214.

The Cosmetically Acceptable Vehicle

The composition according to the invention also comprises a cosmeticallyacceptable vehicle, the selection of which will depend on the requiredproduct form of the composition. Typically, the vehicle will be chosenfrom diluents, dispersants or carriers for the 2-hydroxyalkenoic acid,so as to ensure an even distribution of it when applied to the skin.

Compositions according to this invention can include water as a vehicle,usually with at least one other cosmetically-acceptable vehicle.

Vehicles other than water that can be used in compositions according tothe invention can include liquids or solids as emollients, solvents,humectants, thickeners and powders. Examples of each of these types ofvehicles, which can be used singly or as mixtures of one or morevehicles, are as follows:

Emollients, such as stearyl alcohol, glyceryl monoricinoleate, glycerylmonostearate, propane-1,2-diol, butane-1,3-diol, mink oil, cetylalcohol, isopropyl isostearate, stearic acid, isobutyl palmitate,isocetyl stearate, oleyl alcohol, isopropyl laurate, hexyl laurate,decyl oleate, octadecan-2-ol, isocetyl alcohol, eicosanyl alcohol,behenyl alcohol, cetyl palmitate, silicone oils such asdimethylpolysiloxane, di-n-butyl sebacate, isopropyl myristate,isopropyl palmitate, isopropyl stearate, butyl stearate, polythyleneglycol, triethylene glycol, lanolin, cocoa butter, corn oil, cotton seedoil, tallow, lard, olive oil, palm kernel oil, rapeseed oil, safflowerseed oil, soybean oil, sunflower seed oil, olive oil, sesame seed oil,coconut oil, arachis oil, castor oil, acetylated lanolin alcohols,petroleum, mineral oil, butyl myristate, isostearic acid, palmitaticacid, isopropyl linoleate, lauryl lactate, myristyl lactate, decyloleate, myristyl myristate;

Propellants, such as trichlorofluoromethane, dichlorodifluoromethane,dichlorotetrafluoroethane, monochlorodifluoromethane,trichlorotrifluoroethane, propane, butane, isobutane, dimethyl ether,carbon dioxide, nitrous oxide;

Solvents, such as ethyl alcohol, methylene chloride, isopropanol,acetone, castor oil, ethylene glycol monoethyl ether, diethylene glycolmonobutyl ether, diethylene glycol monoethyl ether, dimethyl sulphoxide,dimethyl formamide, tetrahydrofuran;

Humectants, such as glycerin, sorbitol, sodium2-pyrrolidone-5-carboxylate, soluble collagen, dibutyl phthalate,gelatin;

Powders, such as chalk, talc, fullers earth, kaolin, starch, gums,colloidal silicon dioxide, sodium polyacrylate, tetra alkyl and/ortrialkyl aryl ammonium smectites, chemically modified magnesiumaluminium silicate, organically modified montmorillonite clay, hydratedaluminium silicate, fumed silica, carboxyvinyl polymer, sodiumcarboxymethyl cellulose, ethylene glycol monostearate.

The cosmetically acceptable vehicle will usually form from 10 to 99.9%,preferably from 50 to 99% by weight of the composition, and can, in theabsence of other cosmetic adjuncts, form the balance of the composition.

Cosmetic Adjuncts

Examples of other conventional adjuncts, some of which can also functionas vehicles, that may optionally be employed, include volatile andnon-volatile silicones; silicone polymers; preservatives, such aspara-hydroxy benzoate esters; humectants, such as butane-1,3 -diol,glycerol, sorbitol, polyethylene glycol; stabilisers, such as sodiumchloride or ammonium chloride; buffer system, such as lactic acidtogether with a base such as sodium hydroxide; oils and waxes, such asavocado oil, Evening Primrose oil, sunflower oil, beeswax, ozokeritewax, paraffin wax, lanolin, lanolin alcohol; emollients; thickeners;activity enhancers; colourants; whiteners; perfumes; emulsifiers;sunscreens; bactericides and water.

Cosmetic adjuncts can form up to 50% by weight of the composition andcan conveniently form the balance of the composition.

Process for preparing the composition

The invention also provides a process for the preparation of acomposition for topical application to human skin which comprises thestep of incorporating the 2-hydroxyalkenoic acid, as herein defined,into the composition, together with a cosmetically acceptable vehicle.

Use of the composition

The composition according to the invention is intended primarily as aproduct for topical application to human skin, particularly dry skin,when repeated application can alleviate the dry condition, and restorethe skin to a more natural, soft, supple, healthy state. The compositioncan also be used to treat the hair, including the scalp, and finger andtoe nails.

In use, a small quantity of the composition, for example from 1 to 5 ml,is applied to the affected area of skin, hair or nails, from a suitablecontainer or applicator and, if necessary, it is then spread over and/orrubbed into the skin, hair or nails using the hand or fingers or asuitable device.

PRODUCT FORMS AND PACKAGING

The topical skin treatment composition of the invention can beformulated as a fluid, for example in a product such as a lotion, withor without an applicator such as a roll-ball applicator, or a propellantdriven aerosol device or a container fitted with a pump to dispense thecomposition, for example as a mousse or simply for storage in anon-deformable bottle or squeeze container. Alternatively, thecomposition of the invention may be solid for example, as a bar ortablet, such as a soap bar, or semi-solid, for example as a cream,lotion, gel or ointment, for use in conjunction with a suitableapplicator, or simply for storage in a tube or lidded jar.

The invention accordingly also provides a closed container containing acosmetically acceptable composition as herein defined.

EVIDENCE OF THE SUPERIORITY OF THE INVENTION

The following experiments compare the extensibility of the stratumcorneum when treated either with the 2-hydroxyalkenoic acid of theinvention or with certain corresponding 2-hydroxyalkanoic acids.

Measurements of extensibility were made as described in EP-A 0 007 785.For each sample of stratum corneum, an extensibility ratio wascalculated as the ratio of the extensibility measurement for a treatedsample to the measurement for an untreated control sample.

EXPERIMENT 1

In accordance with this technique, an in vitro extensibility study wascarried out on stratum corneum samples from guinea pig foot pads.Measurements of extensibility were made at a relative humidity of 62%and a temperature of 22° C. on batches of six samples of stratumcorneum. These samples were treated with 0.06M aqueous solution of anacid maintained at pH 4.0 with sodium hydroxide.

The results are detailed in Table 1 below.

                  TABLE 1                                                         ______________________________________                                        All results are at 0.06M concentration and at pH 4.0                                             Extensibility                                                                            Relative                                        Acid               Ratio      Ratio                                           ______________________________________                                        2-Hydroxyoctanoic  1.30       1.00                                            2-Hydroxypropionic (lactic)                                                                      1.24       0.95                                            2-Hydroxydecanoic  1.24       0.95                                            2-Hydroxydodecanoic                                                                              1.28       0.98                                            2-Hydroxy-4-decenoic                                                                             1.50       1.15                                            2-Hydroxy-4-dodecenoic                                                                           1.46       1.12                                            2-Hydroxy-4,9-decadienoic                                                                        1.72       1.32                                            2-Hydroxy-4,11-dodecadienoic                                                                     1.52       1.17                                            ______________________________________                                    

The value for distilled water at pH 4.0 is approximately unity. It isevident that the use of the 2-hydroxyalkenoic acids leads to an increasein the ratio of up to 32% when compared to the use of the best2-hydroxyalkanoic acid, i.e. 2-hydroxyoctanoic acid.

EXPERIMENT 2

This experiment compares the increase in extensibility conferred byaqueous solutions of acids at low pH. The tests were carried out onheat-separated guinea-pig footpads which were immersed in the requiredsolution at the specified pH value. The extensibility ratios are shownin Table 2.

                  TABLE 2                                                         ______________________________________                                                                       Extensibility                                  Acid          Concn.     pH    Relative                                       ______________________________________                                        2-Hydroxypropionic                                                                          0.20M      2.5   3.00 ± 0.65                                 2-Hydroxyoctanoic                                                                           0.20M      2.5   5.90 ± 0.75                                 2-Hydroxy-13-oxa-4-                                                                         0.12M      2.9   12.35 ± 4.33                                tetradecenoic                                                                 ______________________________________                                    

The extensibility ratio for the 2-hydroxy-13-oxa-4-tetradecenoic acid issignificantly greater at the 99% confidence level than that of the2-hydroxypropionic acid. The elasticity effect of this oxa acid is alsosignificantly greater at the 98% confidence level than that of the2-hydroxyoctanoic acid. Both the shorter acids were evaluated at a lowerpH value and a higher concentration and still appear inferior to the oxaacid.

EXPERIMENT 3

This experiment compares the extensibility increase conferred in-vitroby solutions of several 2-hydroxyalkenoic acids against that conferredby 2-hydroxy octanoic acid. The tests were carried out on heat-separatedguinea-pig footpads which were immersed in the required solutionmaintained at pH 4.0 by the addition of sodium hydroxide solution. Theextensibility ratios for each group of samples are shown in Table 3.

                  TABLE 3                                                         ______________________________________                                                     Extensibility                                                                            Relative  Significance                                Acid         Ratio      Ratio     Level                                       ______________________________________                                        part i)                                                                       All the following results are at 0.06M concentration.                         2-Hydroxy octanoic                                                                         1.30 ± 0.27                                                                           1.00      --                                          2-Hydroxy-13-oxa-                                                                          2.53 ± 0.72                                                                           1.95      98%                                         4-pentadecenoic                                                               2-Hydroxy-14-oxa-                                                                          3.02 ± 0.82                                                                           2.23      99%                                         4-pentadecenoic                                                               2-Hydroxy-14-oxa-                                                                          2.46 ± 0.63                                                                           1.89      99%                                         4-hexadecenoic                                                                2-Hydroxy-14,17-                                                                           3.73 ± 1.78                                                                           2.87      95%                                         dioxa-4-                                                                      octadecenoic                                                                  ______________________________________                                        Part ii)                                                                      All the following results are at 0.12M concentration.                         2-Hydroxy octanoic                                                                         2.79 ± 0.71                                                                           1.00      --                                          2-Hydroxy-13-oxa-4-                                                                        4.49 ± 0.83                                                                           1.61      98%                                         tetradecenoic                                                                 2-Hydroxy-13-oxa-4-                                                                        4.88 ± 1.22                                                                           1.75      98%                                         pentadecenoic                                                                 2-Hydroxy-14-oxa-4-                                                                        4.44 ± 0.47                                                                           1.59      99%                                         hexadecenoic                                                                  2-Hydroxy-14,17-                                                                           5.44 ± 1.47                                                                           1.95      98%                                         dioxa-4-                                                                      octadecenoic                                                                  ______________________________________                                    

EXPERIMENT 4

This experiment compares the elasticity effect conferred by an aqueoussolution of an unsaturated acid with that conferred by an aqueoussolution of the saturated equivalent acid. The evaluation was performedon heat-separated guinea-pig footpads which were immersed in therequired solution maintained at pH 4.0. The results are shown in Table4.

                  TABLE 4                                                         ______________________________________                                        All the following results are at 0.12M concentration.                                            Extensibility                                                                             Relative                                       Acid               Ratio       Ratio                                          ______________________________________                                        2-Hydroxy-14-oxa pentadecanoic                                                                   1.76 ± 0.54                                                                            --                                             2-Hydroxy-14-oxa-4-                                                                              4.88 ± 1.22                                                                            2.77                                           pentadecenoic                                                                 ______________________________________                                    

The extensibility ratio for the 2-hydroxyalkenoic acid[2-hydroxy-14-oxa-4-pentadecenoic acid] is significantly greater at the99% confidence level than that of the corresponding 2-hydroxyalkanoicacid [2-hydroxy-14-oxa-pentadecanoic acid].

EXAMPLES Cosmetic Compositions

The invention is further illustrated by the following examples.

EXAMPLE 6

The example illustrates an oil-continuous (W/O) cream containing2-hydroxy-4-tetradecenoic acid.

    ______________________________________                                        Ingredients          % w/w                                                    ______________________________________                                        Silicone oils        24.00                                                    Whitener             0.15                                                     Humectants           5.00                                                     2-Hydroxy-4 tetradecenoic acid                                                                     1.00                                                     Lactic acid          5.00                                                     Potassium hydroxide  4.00                                                     Water                60.85                                                                         100.00                                                   ______________________________________                                    

The skin cream, having a pH value of 5, is made by the process, asherein described, by adding gradually to a mixture of silicones andwhitener an aqueous mixture of the remaining ingredients andhomogenising.

EXAMPLE 7

This example illustrates an oil-continuous w/o cream containing2-hydroxy-13-oxa-4-pentadecenoic acid, evening primrose oil andsunscreens.

    ______________________________________                                        Ingredients            % w/w                                                  ______________________________________                                        Silicone oils          25.00                                                  Whitener               0.15                                                   Evening Primrose Oil   3.00                                                   Humectants             5.00                                                   Sunscreens             4.00                                                   2-Hydroxy-13-oxa-4-pentadecenoic acid                                                                1.50                                                   Sodium hydroxide       2.00                                                   Sodium chloride        2.00                                                   Lactic acid            5.00                                                   Water                  52.35                                                                         100.00                                                 ______________________________________                                    

The skin cream, having a pH value of 4.5, is made by the process, asherein described, by adding gradually to a mixture of silicones andwhitener an aqueous mixture of the remaining ingredients andhomogenising.

EXAMPLE 8

This example illustrates a oil-continuous (w/o) gel containing2-hydroxy-4-dodecenoic acid.

    ______________________________________                                        Ingredients         % w/w                                                     ______________________________________                                        Emulsifiers         20.00                                                     Silicone oils       20.00                                                     Humectant           11.00                                                     2-Hydroxy-4-dodecenoic acid                                                                       1.00                                                      Sodium hydroxide    4.55                                                      Lactic acid         5.00                                                      Water               38.45                                                                         100.00                                                    ______________________________________                                    

The gel, having a pH value of 5.5, is made by the process, as hereindescribed, by adding to the silicone oils an aqueous mixture of theremaining ingredients and homogenising.

EXAMPLE 9

This example illustrates a water-continuous (o/w) cream containing a2-hydroxy-4-decenoic acid.

    ______________________________________                                        Ingredients        % w/w                                                      ______________________________________                                        Thickener          0.50                                                       Whitener           0.15                                                       Humectant          13.50                                                      Emulsifiers        10.35                                                      Silicone oil       7.60                                                       2-Hydroxy-4-decenoic acid                                                                        1.00                                                       Sodium Hydroxide   5.00                                                       Lactic Acid        3.00                                                       Water              58.90                                                                         100.00                                                     ______________________________________                                    

The skin cream, having a pH value of 4, is made by the process, asherein described, by adding to a heated mixture of the thickener,humectant and 75% of the water. The remaining ingredients are added asan aqueous mixture with further homogenising.

EXAMPLE 10

This example illustrates a water-continuous (o/w) cream containing2-hydroxy-4,11-dodecadienoic acid, evening primrose oil and sunscreens.

    ______________________________________                                        Ingredients           % w/w                                                   ______________________________________                                        Thickener             0.50                                                    Whitener              0.20                                                    Humectant             10.00                                                   Evening Primrose Oil  2.00                                                    Sunscreens            3.00                                                    Emulsifiers           10.50                                                   Silicone oil          7.60                                                    2-Hydroxy-4,11-dodecadienoic acid                                                                   1.00                                                    Triethanolamine       6.00                                                    Lactic acid           4.00                                                    Water                 55.20                                                                         100.00                                                  ______________________________________                                    

The skin cream, having a pH value of 6, is made by the process, asherein described, by adding to a heated mixture of emulsifiers, siliconeoil and whitener a mixture of the thickener, humectant and 75% of thewater and homogenising. The remaining ingredients are added as anaqueous mixture with further homogenising.

EXAMPLE 11

The example illustrates a night cream containing2-hydroxy-4,21-docosadienoic acid and beeswax.

    ______________________________________                                        Incredients          % w/w                                                    ______________________________________                                        Silicone oil         21.00                                                    Emulsifiers          15.25                                                    Beeswax              8.00                                                     Lanolin              2.50                                                     2-Hydroxy-4,21-docosadienic acid                                                                   2.00                                                     Potassium hydroxide  5.00                                                     Water                46.25                                                                         100.00                                                   ______________________________________                                    

The night cream, having a pH value of 6.5, is made by the process, asherein described, by adding to a mixture of emulsifiers, silicone oil,beeswax and lanolin, a mixture of the remaining ingredients andhomogenising.

EXAMPLE 12

This example illustrates a lotion suitable for application to the handscontaining 2-hydroxy-4-octenoic acid and lanolin.

    ______________________________________                                        Ingredient         %                                                          ______________________________________                                        Emulsifiers        10.00                                                      Lanolin            2.50                                                       2-Hydroxy-4-octenoic acid                                                                        3.00                                                       Trethanolamine     4.50                                                       Water              80.00                                                                         100.00                                                     ______________________________________                                    

EXAMPLE 13

This example illustrates a water-continuous (o/w) hand and body lotioncontaining 2-hydroxy-17-oxa-4-octadecenoic acid.

    ______________________________________                                        Ingredient             %                                                      ______________________________________                                        Emulsifiers            3.00                                                   Silicone oil           5.00                                                   Thickener              0.35                                                   Humectant              9.45                                                   2-Hydroxy-17-oxa-4-octadecenoic acid                                                                 1.50                                                   Ammonium hydroxide     3.95                                                   Ammonium chloride      2.00                                                   Water                  74.75                                                                         100.00                                                 ______________________________________                                    

EXAMPLE 14

This example illustrates a wash-off/wipe-off cleansing cream containing2-hydroxy-4-hexenoic acid and chamomile.

    ______________________________________                                        Ingredient         %                                                          ______________________________________                                        Mineral oil        10.00                                                      Emulsifier         3.00                                                       Chamomile distillate                                                                             0.50                                                       2-Hydroxy-4-hexenoic acid                                                                        1.00                                                       Triethanolamine    2.80                                                       Water              82.70                                                                         100.00                                                     ______________________________________                                    

EXAMPLE 15

This example illustrates a wash-off/wipe-off cleansing lotion containing2-hydroxy-4,15-hexadecadienoic acid and beeswax.

    ______________________________________                                        Ingredient             % w/w                                                  ______________________________________                                        Mineral oil            45.00                                                  Emulsifier             3.20                                                   Beeswax                8.00                                                   Thickener              10.00                                                  Perfume                0.20                                                   2-Hydroxy-4,15-hexadecadienoic acid                                                                  1.00                                                   Triethanolamine        4.00                                                   Water                  28.60                                                                         100.00                                                 ______________________________________                                    

The cleansing lotion, having a pH of 5.5, is made by the process, asherein described, by adding to a mixture of emulsifier, mineral oil andbeeswax a mixture of the remaining ingredients and homogenising.

EXAMPLE 16

The example illustrates a facial-washing foam containing2-hydroxy-23,26-dioxa-4-octacosenoic acid and azulene.

    ______________________________________                                        Ingredient             % w/w                                                  ______________________________________                                        Emulsifier             20.00                                                  Thickener              3.00                                                   Foam Booster           25.00                                                  Humectant              10.00                                                  Azulene crystals       0.25                                                   Bentone                0.50                                                   2-Hydroxy-23,26-dioxa-4-octacosenoic                                                                 2.50                                                   acid                                                                          Potassium hydroxide    4.50                                                   Water                  34.25                                                                         100.00                                                 ______________________________________                                    

EXAMPLE 17

This example illustrates a conventional soap bar containing2-hydroxy-4-docosenoic acid.

    ______________________________________                                        Ingredient          % w/w                                                     ______________________________________                                        Anionic detergent   18.00                                                     Foam aid            8.00                                                      Sodium hydroxide    12.00                                                     Hardening agent     2.00                                                      Alkaline silicate   2.00                                                      Calcite             12.00                                                     Talc                10.00                                                     2-Hydroxy-4-docosenoic acid                                                                       2.00                                                      Water               34.00                                                                         100.00                                                    ______________________________________                                    

EXAMPLE 18

This example illustrates an all-purpose face-mask containing2-hydroxy-4-hexacosenoic acid and phytoconcentrol camomile.

    ______________________________________                                        Ingredient           % w/w                                                    ______________________________________                                        Kaolin               30.00                                                    Mineral oil          10.00                                                    Paraffin wax         10.00                                                    Bentonite            4.00                                                     2-Hydroxy-4-hexacosenoic acid                                                                      1.40                                                     Sodium hydroxide     4.20                                                     Phytoconcentrol camomile                                                                           0.25                                                     Water                40.15                                                                         100.00                                                   ______________________________________                                    

The mask is made by the process, as herein described, by blending themixture of the ingredients.

EXAMPLE 19

This example illustrates a solution used to condition hair containing2-hydroxy-4-hexadecenoic acid.

    ______________________________________                                        Ingredient           % w/w                                                    ______________________________________                                        Emulsifier           0.80                                                     2-Hydroxy-4-hexadecenoic acid                                                                      0.50                                                     Sodium chloride      0.50                                                     Sodium hydroxide     2.00                                                     Water                96.20                                                                         100.00                                                   ______________________________________                                    

EXAMPLE 20

The example illustrates a gel suitable for treating hair containing2-hydroxy-19-methyl-18-oxa-4-eicosenoic acid and alpha-bisabolol.

    ______________________________________                                        Ingredient           % w/w                                                    ______________________________________                                        Emulsifiers          20.00                                                    Silicone oil         20.00                                                    Humectant            11.00                                                    Lactic acid          5.00                                                     2-Hydroxy-19-methyl-18-oxa-4-                                                                      1.50                                                     eicosenoic acid                                                               Alpha-bisabolol      0.20                                                     Triethanolamine      4.55                                                     Fragrance            0.10                                                     Water                37.65                                                                         100.00                                                   ______________________________________                                    

EXAMPLE 21

The example illustrates a nail strenthener suitable for treating drynessand brittleness, containing 2-hydroxy-4-tetracosenoic acid.

    ______________________________________                                        Ingredient           % w/w                                                    ______________________________________                                        Humectant            10.00                                                    Mineral oil          10.00                                                    2-Hydroxy-4-tetracosenoic acid                                                                     2.00                                                     Potassium hydroxide  4.50                                                     Water                73.50                                                                         100.00                                                   ______________________________________                                    

EXAMPLE 22

The example illustrates a lotion suitable for treatment of nails,containing 2-hydroxy-4,9-decadienoic acid and beeswax.

    ______________________________________                                        Ingredient           % w/w                                                    ______________________________________                                        Propane-1,2-diol     50.00                                                    Ethanol              10.00                                                    Beeswax              5.00                                                     2-Hydroxy-4,9-decadienoic acid                                                                     3.00                                                     Sodium chloride      3.00                                                     Sodium hydroxide     4.25                                                     Water                24.75                                                                         100.00                                                   ______________________________________                                    

This lotion, having a pH value of 4.3, is made by the process, as hereindescribed, by homogenising the mixture of the ingredients.

We claim:
 1. A cosmetically acceptable composition for topicalapplication to human skin or hair, which comprises:i. from 0.1 to 99.9%by weight of a 2-hydroxyalkenoic acid having the structure (20)##STR15## where R" is selected from the group consisting of:a. C_(w)H_(2w), b. C_(y) H_(2y-1), and c. C_(y) H_(2y) OZ whereZ is selectedfrom the group consisting of: H, R" and (CH₂)_(n) OR" R" is selectedfrom the group consisting of: C_(m) H_(2m+1) and (CH₂)_(n) OC_(m)H_(2m+1) ; w is an integer of from 1 to 25 y is an integer of from 2 to25 m is an integer of from 1 to 4 n is an integer of from 1 to 6; andii. from 0.1 to 99.9% by weight of a cosmetically acceptable vehicle forthe acid.
 2. A composition according to claim 1, in which the2-hydroxyalkenoic acid is selected from the group consistingof:2-hydroxy-4 -hexenoic acid 2-Hydroxy-4-heptenoic acid2-hydroxy-4-octenoic acid 2-Hydroxy 4-nonenoic acid 2-hydroxy-4-decenoicacid 2-Hydroxy-4-undecenoic acid 2-hydroxy-4 -dodecenoic acid 2-Hydroxy4-tridecenoic acid 2-Hydroxy-4-tetradecenoic acid2-Hydroxy-4-pentadecenoic acid 2-Hydroxy-4-hexadecenoic acid2-Hydroxy-4-heptadecenoic acid 2-Hydroxy-4-octadecenoic acid2-Hydroxy-4-nonadecenoic acid 2-Hydroxy-4-eicosenoic acid2-Hydroxy-4-heneicosenoic acid 2-Hydroxy-4-docosenoic acid2-Hydroxy-4-tricosenoic acid 2-Hydroxy-4-tetracosenoic acid2-Hydroxy-4-pentacosenoic acid 2-Hydroxy-4-hexacosenoic acid2-Hydroxy-4-heptacosenoic acid 2-Hydroxy-4-octacosenoic acid2-Hydroxy-4-nonacosenoic acid, and 2-Hydroxy-4-triacontencoic acid.
 3. Acomposition according to claim 1, in which the 2-hydroxyalkenoic acid isselected from the group consisting of:2-Hydroxy-4,7-octadienoic acid2-Hydroxy-4,9-decadienoic acid 2-Hydroxy-4,10-undecadienoic acid2-Hydroxy 4,11-dodecadienoic acid 2-Hydroxy-4,13-tetradecadienoic acid2-Hydroxy-4,15-hexadecadienoic acid 2-Hydroxy-4,17-octadecadienoic acid2-Hydroxy 4,19-eicosadienoic acid 2-Hydroxy 4,21-docosadienoic acid2-Hydroxy-4,23-tetracosadienoic acid 2-Hydroxy-4,25-hexacosadienoic acid2-Hydroxy-4,27-octacosadienoic acid, and 2-Hydroxy-4,29-triacontadienoicacid.
 4. A composition according to claim 1, in which the2-hydroxyalkenoic acid is selected from the group consistingof:2-Hydroxy-6-oxa-4-heptenoic acid 2-Hydroxy-7-oxa-4-octenoic acid2-Hydroxy-9 oxa-4-decenoic acid 2-Hydroxy-9-oxa-4-undecenoic acid2-Hydroxy-11-oxa-4-dodecenoic acid 2-Hydroxy-13-oxa-4-tetradecenoic acid2-Hydroxy-13-oxa-4-pentadecenoic acid 2-Hydroxy-14-oxa-4-pentadecenoicacid 2-Hydroxy-13-oxa-14-methyl-4-pentadecenoic acid2-Hydroxy-11,14-dioxa-4-pentadecenoic acid2-Hydroxy-13-oxa-4-hexadecenoic acid 2-Hydroxy-14-oxa-4-hexadecenoicacid 2-Hydroxy-15-oxa-4-hexadecenoic acid2-Hydroxy-17-oxa-4-octadecenoic acid2-Hydroxy-14,17-dioxa-4-octadecenoic acid 2-Hydroxy-18-oxa-4-eicosenoicacid 2-Hydroxy-18-oxa-19-methyl-4-eicosenoic acid2-Hydroxy-19-oxa-4-docosenoic acid 2-Hydroxy-18,21-dioxa-4-tricosenoicacid 2-Hydroxy-22-oxa-4-tetracosenoic acid2-Hydroxy-25-oxa-4-hexacosenoic acid 2-Hydroxy-24-oxa-4-heptacosenoicacid 2-Hydroxy-25-oxa-4-octacosenoic acid2-Hydroxy-23,26-dioxa-4-octacosenoic acid, and2-Hydroxy-29-oxa-4-triacontenoic acid.
 5. A composition according toclaim 1, in which the 2-hydroxyalkenoic acid forms from 0.5 to 10% byweight.
 6. A composition according to claim 1, which is an emulsion. 7.A composition according to claim 1, which is a lotion.
 8. A compositionaccording to claim 6 which is a cream.